Justin Timberlake may be back together with actress Jessica Biel, but that didn’t stop him from going out with another woman. Timberlake was snapped alongside leggy blonde Marine Cpl. Kelsey de Santis, his date to the Instructor Battalion Marine Corps Ball in Richmond, Va.

De Santis asked Timberlake to the ball via YouTube in July, following the lead of Sgt. Scott Moore, who had asked Timberlake’s “Friends with Benefits” co-star Mila Kunis to his ball in a video that quickly went viral. When Timberlake publicly ribbed Kunis about the invitation, saying that she needed to attend “for your country,” de Santis took to YouTube with her own invitation for Timberlake.

“So Justin, You want to call out my girl, Mila? Well, I’m going to call you out and ask you to come to the Marine Corps ball with me on November 12,” de Santis said in a video that was viewed close to 2 million times. “If you can’t go, all I have to say is cry me a river.”

In her YouTube video, de Santis appeared gruff and no-nonsense in fatigues and no makeup. But the dimpled blonde sure cleaned up nice, wearing a skirt suit uniform bedecked with several medals over her heart. De Santis, who is a mixed martial arts expert, later changed into a figure-hugging blue beaded number. Timberlake sported a navy blue bow tie with his dapper black suit.

Timberlake posted on his blog yesterday that attending the ball Saturday night “changed my life.” The pop superstar wrote, “I glanced around the room at young men and women, spouses and soldiers … I felt so proud to be there. I felt like I was getting a chance to be among my heroes … To all of you that serve every day for us, ensuring our freedom, I say: my deepest gratitude to you.”

He also had kind words to say about his date. “She seemed to me to be so humble and honest … ‘Are you ok?’ she asked 2 or 3 times. ‘I hope you are having fun. I know you will once my crew of friends get here to the table.’ I have to tell you, it’s not every day that I meet a 23 year old girl and she’s more worried about if I’m having fun.”

Mila Kunis has not wimped out on attending the ball with Moore — Timberlake simply beat her to the punch. Kunis’ publicist says that she will be attending on Nov. 18 in Greenville, NC.